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Abstract:

Reactors for conducting thermochemical processes with solar heat input,
and associated systems and methods. A representative system includes a
reactor having a reaction zone, a reactant source coupled in fluid in
communication with the reactant zone, and a solar concentrator having at
least one concentrator surface positionable to direct solar energy to a
focal area. The system can further include an actuator coupled to the
solar concentrator to move the solar concentrator relative to the sun,
and a controller operatively coupled to the actuator. The controller can
be programmed with instructions that direct the actuator to position the
solar concentrator to focus the solar energy on the reaction zone when
the solar energy is above a threshold level, and point to a location in
the sky having relatively little radiant energy to cool an object when
the solar energy is below the threshold level.

Claims:

1. A reactor system for processing a reactant, comprising: a reactor
having a reaction zone; a reactant source coupled in fluid communication
with the reaction zone of the reactor; a solar concentrator having at
least one concentrator surface positionable to direct solar energy to a
focal area; an actuator coupled to the solar concentrator to move the
solar concentrator relative to the sun; and a controller operatively
coupled to the actuator, the controller being programmed with
instructions that, when executed: direct the actuator to position the
solar concentrator to focus the solar energy on the reaction zone when
the solar energy is above a threshold level; and direct the actuator to
position the solar concentrator to point to a location in the sky having
relatively little radiant energy to cool an object positioned at the
focal area when the solar energy is below the threshold level.

2-31. (canceled)

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to pending U.S. Provisional
Application 61/304,403, filed Feb. 13, 2010 and incorporated herein by
reference. To the extent the foregoing application and/or any other
materials incorporated herein by reference conflict with the disclosure
presented herein, the disclosure herein controls.

TECHNICAL HELD

[0002] The present technology is directed generally to reactors for
conducting thermochemical processes with solar heat input, and associated
systems and methods. In particular embodiments, such reactors can be used
to produce clean-burning, hydrogen-based fuels from a wide variety of
feedstocks, and can produce structural building blocks from carbon and/or
other elements that are released when forming the hydrogen-based fuels.

BACKGROUND

[0003] Renewable energy sources such as solar, wind, wave, falling water,
and biomass-based sources have tremendous potential as significant energy
sources, but currently suffer from a variety of problems that prohibit
widespread adoption. For example, using renewable energy sources in the
production of electricity is dependent on the availability of the
sources, which can be intermittent. Solar energy is limited by the sun's
availability (i.e., daytime only), wind energy is limited by the
variability of wind, falling water energy is limited by droughts, and
biomass energy is limited by seasonal variances, among other things. As a
result of these and other factors, much of the energy from renewable
sources, captured or not captured, tends to be wasted.

[0004] The foregoing inefficiencies associated with capturing and saving
energy limit the growth of renewable energy sources into viable energy
providers for many regions of the world, because they often lead to high
costs of producing energy. Thus, the world continues to rely on oil and
other fossil fuels as major energy sources because, at least in part,
government subsidies and other programs supporting technology
developments associated with fossil fuels make it deceptively convenient
and seemingly inexpensive to use such fuels. At the same time, the
replacement cost for the expended resources, and the costs of environment
degradation, health impacts, and other by-products of fossil fuel use are
not included in the purchase price of the energy resulting from these
fuels.

[0005] In light of the foregoing and other drawbacks currently associated
with sustainably producing renewable resources, there remains a need for
improving the efficiencies and commercial viabilities of producing
products and fuels with such resources

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a partially schematic, partial cross-sectional
illustration of a system having a solar concentrator configured in
accordance with an embodiment of the present technology.

[0007]FIG. 2 is a partially schematic, partial cross-sectional
illustration of an embodiment of the system shown in FIG. 1 with the
solar concentrator configured to emit energy in a cooling process, in
accordance with an embodiment of the disclosure.

[0008] FIG. 3 is a partially schematic, partial cross-sectional
illustration of a system having a movable solar concentrator dish in
accordance with an embodiment of the disclosure.

[0009]FIG. 4 is a partially schematic, isometric illustration of a system
having a trough-shaped solar concentrator in accordance with an
embodiment of the disclosure.

[0010]FIG. 5 is a partially schematic illustration of a system having a
Fresnel lens concentrator in accordance with an embodiment of the
disclosure.

[0011]FIG. 6 is a partially schematic illustration of a reactor having a
radiation control structure and redirection components configured in
accordance with an embodiment of the present technology.

DETAILED DESCRIPTION

1. Overview

[0012] Several examples of devices, systems and methods for conducting
reactions driven by solar energy are described below. Reactors in
accordance with particular embodiments can collect solar energy during
one phase of operation and use the collection device to reject heat
during another phase of operation. Such reactors can be used to produce
hydrogen fuels and/or other useful end products. Accordingly, the
reactors can produce clean-burning fuel and can re-purpose carbon and/or
other constituents for use in durable goods, including polymers and
carbon composites. Although the following description provides many
specific details of the following examples in a manner sufficient to
enable a person skilled in the relevant art to practice, make and use
them, several of the details and advantages described below may not be
necessary to practice certain examples of the technology. Additionally,
the technology may include other examples that are within the scope of
the claims but are not described here in detail.

[0013] References throughout this specification to "one example," "an
example," "one embodiment" or "an embodiment" mean that a particular
feature, structure, process or characteristic described in connection
with the example is included in at least one example of the present
technology. Thus, the occurrences of the phrases "in one example," "in an
example," "one embodiment" or "an embodiment" in various places
throughout this specification are not necessarily all referring to the
same example. Furthermore, the particular features, structures, routines,
steps or characteristics may be combined in any suitable manner in one or
more examples of the technology. The headings provided herein are for
convenience only and are not intended to limit or interpret the scope or
meaning of the claimed technology.

[0014] Certain embodiments of the technology described below may take the
form of computer-executable instructions, including routines executed by
a programmable computer or controller. Those skilled in the relevant art
will appreciate that the technology can be practiced on computer or
controller systems other than those shown and described below. The
technology can be embodied in a special-purpose computer, controller, or
data processor that is specifically programmed, configured or constructed
to perform one or more of the computer-executable instructions described
below. Accordingly, the terms "computer" and "controller" as generally
used herein refer to any data processor and can include Internet
appliances, hand-held devices, multi-processor systems, programmable
consumer electronics, network computers, mini-computers, and the like.
The technology can also be practiced in distributed environments where
tasks or modules are performed by remote processing devices that are
linked through a communications network. Aspects of the technology
described below may be stored or distributed on computer-readable media,
including magnetic or optically readable or removable computer discs as
well as media distributed electronically over networks. In particular
embodiments, data structures and transmissions of data particular to
aspects of the technology are also encompassed within the scope of the
present technology. The present technology encompasses both methods of
programming computer-readable media to perform particular steps, as well
as executing the steps.

[0015] A reactor system in accordance with a particular embodiment
includes a reactor having a reaction zone, a reactant source coupled in
fluid communication with the reaction zone, and a solar collector having
a least one concentrator surface positionable to direct solar energy to a
focal area. The system can further include an actuator coupled to the
solar concentrator to move the solar concentrator relative to the sun,
and a controller operatively coupled to the actuator to control its
operation. The controller can be programmed with instructions that, when
executed, direct the actuator to position the solar concentrator to focus
the solar energy on the reaction zone when the solar energy is above a
threshold level (e.g. during the day). When the solar energy is below the
threshold level, the controller can direct the actuator to position the
solar concentrator to point to a location in the sky having relatively
little radiant energy to cool an object positioned at the focal area.

[0016] A system in accordance with another embodiment of the technology
includes a reactor, a reactant source, a solar concentrator, and a first
actuator coupled to the solar concentrator to move the solar concentrator
relative to the sun. The system can further include a radiation control
structure positioned between a concentrator surface of the solar
concentrator and its associated focal area. The radiation control
structure has first surface and a second surface facing away from the
first surface, each with a different absorptivity and emissivity. In
particular, the first surface can have a first radiant energy
absorptivity and a first radiant energy emissivity, and the second
surface can have a second radiant energy absorptivity less than the first
radiant energy absorptivity, and a second radiant energy emissivity
greater than the first radiant energy emissivity. The system can further
include a second actuator coupled to the radiation control structure to
change the structure from a first configuration in which the first
surface faces toward the concentrator surface, and a second configuration
in which the second surface faces toward the concentrator surface. In
particular embodiments, the system can still further include a controller
that directs the operation of the radiation control structure depending
upon the level of solar energy directed by the solar concentrator.

[0017] A method in accordance with a particular embodiment of the
technology includes concentrating solar energy with a solar concentrator,
directing the concentrated solar energy to a reaction zone positioned at
a focal area of the solar concentrator, and at the reaction zone,
dissociating a hydrogen donor into dissociation products via the
concentrated solar energy. From the dissociation products, the method can
further include providing at least one of a structural building block
(based on at least one of carbon, nitrogen, boron, silicon sulfur, and a
transition metal) and hydrogen-based fuel. In further particular
embodiments, the method can further include taking different actions
depending upon whether the solar energy is above or below a threshold
level. For example, when the solar energy is above a threshold level, it
can be directed to the reaction zone, and when it is below the threshold
level, the solar concentrator can be pointed away from the sun to a
location in the sky having relatively little radiative energy to cool the
structural building block and/or the hydrogen based fuel.

2. Representative Reactors and Associated Methodologies

[0018] FIG. 1 is a partially schematic, partial cross-sectional
illustration of a system 100 having a reactor 110 coupled to a solar
concentrator 120 in accordance with the particular embodiment of the
technology. In one aspect of this embodiment, the solar concentrator 120
includes a dish 121 mounted to pedestal 122. The dish 121 can include a
concentrator surface 123 that receives incident solar energy 126, and
directs the solar energy as focused solar energy 127 toward a focal area
124. The dish 121 can be coupled to a concentrator actuator 125 that
moves the dish 121 about at least two orthogonal axes in order to
efficiently focus the solar energy 126 as the earth rotates. As will be
described in further detail below, the concentrator actuator 125 can also
be configured to deliberately position the dish 121 to face away from the
sun during a cooling operation.

[0019] The reactor 110 can include one or more reaction zones 111, shown
in FIG. 1 as a first reaction zone 111a and second reaction zone 111b. In
a particular embodiment, the first reaction zone 111a is positioned at
the focal area 124 to receive the focused solar energy 127 and facilitate
a dissociation reaction or other endothermic reaction. Accordingly, the
system 100 can further include a distribution/collection system 140 that
provides reactants to the reactor 110 and collects products received from
the reactor 110. In one aspect of this embodiment, the
distribution/collection system 140 includes a reactant source 141 that
directs a reactant to the first reaction zone 111a, and one or more
product collectors 142 (two are shown in FIG. 1 as a first product
collector 142a and a second product collector 142b) that collect products
from the reactor 110. When the reactor 110 includes a single reaction
zone (e.g. the first reaction zone 111a) the product collectors 142a,
142b can collect products directly from the first reaction zone 111a. In
another embodiment, intermediate products produced at the first reaction
zone 111a are directed to the second reaction zone 111b. At the second
reaction zone 111b, the intermediate products can undergo an exothermic
reaction, and the resulting products are then delivered to the product
collectors 142a, 142b along a product flow path 154. For example, in a
representative embodiment, the reactant source 141 can include methane
and carbon dioxide, which are provided (e.g., in an individually
controlled manner) to the first reaction zone 111a and heated to produce
carbon monoxide and hydrogen. The carbon monoxide and hydrogen are then
provided to the second reaction zone 111b to produce methanol in an
exothermic reaction. Further details of this arrangement and associated
heat transfer processes between the first reaction zone 111a and second
reaction zone 111b are described in more detail in co-pending U.S.
application Ser. No. ______ titled "REACTOR VESSELS WITH PRESSURE AND
HEAT TRANSFER FEATURES FOR PRODUCING HYDROGEN-BASED FUELS AND STRUCTURAL
ELEMENTS, AND ASSOCIATED SYSTEMS AND METHODS" (Attorney Docket No.
69545.8616US) filed concurrently herewith and incorporated herein by
reference.

[0020] In at least some instances, it is desirable to provide cooling to
the reactor 110, in addition to the solar heating described above. For
example, cooling can be used to remove heat produced by the exothermic
reaction being conducted at the second reaction zone 111b and thus allow
the reaction to continue. When the product produced at the second
reaction zone 111b includes methanol, it may desirable to further cool
the methanol to a liquid to provide for convenient storage and
transportation. Accordingly, the system 100 can include features that
facilitate using the concentrator surface 123 to cool components or
constituents at the reactor 110. In a particular embodiment, the system
100 includes a first heat exchanger 150a operatively coupled to a heat
exchanger actuator 151b that moves the first heat exchanger 150a relative
to the focal area 124. The first heat exchanger 150a can include a heat
exchanger fluid that communicates thermally with the constituents in the
reactor 110, but is in fluid isolation from these constituents to avoid
contaminating the constituents and/or interfering with the reactions
taking place in the reactor 110. The heat exchanger fluid travels around
a heat exchanger fluid flow path 153 in a circuit from the first heat
exchanger 150a to a second heat exchanger 150b and back. At the second
heat exchanger 150b, the heat exchanger fluid receives heat from the
product (e.g. methanol) produced by the reactor 110 as the product
proceeds from the second reaction zone 111b to the
distribution/collection system 140. The heat exchanger fluid flow path
153 delivers the heated heat exchanger fluid back to the first heat
exchanger 150a for cooling. One or more strain relief features 152 in the
heat exchanger fluid flow path 153 (e.g., coiled conduits) facilitate the
movement of the first heat exchanger 150a. The system 100 can also
include a controller 190 that receives input signals 191 from any of a
variety of sensors, transducers, and/or other elements of the system 100,
and, in response to information received from these elements, delivers
control signals 192 to adjust operational parameters of the system 100.

[0021]FIG. 2 illustrates one mechanism by which the heat exchanger fluid
provided to the first heat exchanger 150a is cooled. In this embodiment,
the controller 190 directs the heat exchanger actuator 151 to drive the
first heat exchanger 150a from the position shown in FIG. 1 to the focal
area 124, as indicated by arrows A. In addition, the controller 190 can
direct the concentrator actuator 125 to position the dish 121 so that the
concentrator surface 123 points away from the sun and to an area of the
sky having very little radiant energy. In general, this process can be
completed at night, when it is easier to avoid the radiant energy of the
sun and the local environment, but in at least some embodiments, this
process can be conducted during the daytime as well. A radiant energy
sensor 193 coupled to the controller 190 can detect when the incoming
solar radiation passes below a threshold level, indicating a suitable
time for positioning the first heat exchanger 150a in the location shown
in FIG. 2.

[0022] With the first heat exchanger 150a in the position shown in FIG. 2,
the hot heat transfer fluid in the heat exchanger 150a radiates emitted
energy 128 that is collected by the dish 121 at the concentrator surface
123 and redirected outwardly as directed emitted energy 129. An insulator
130 positioned adjacent to the focal area 124 can prevent the radiant
energy from being emitted in direction other than toward the concentrator
surface 123. By positioning the concentrator surface 123 to point to a
region in space having very little radiative energy, the region in space
can operate as a heat sink, and can accordingly receive the directed
emitted energy 129 rejected by the first heat exchanger 150a. The heat
exchanger fluid, after being cooled at the first heat exchanger 150a
returns to the second heat exchanger 150b to absorb more heat from the
product flowing along the product flow path 154. Accordingly, the
concentrator surface 123 can be used to cool as well as to heat elements
of the reactor 110.

[0023] In a particular embodiment, the first heat exchanger 150a is
positioned as shown in FIG. 1 during the day, and as positioned as shown
in FIG. 2 during the night. In other embodiments, multiple systems 100
can be coupled together, some with the corresponding first heat exchanger
150a positioned as shown in FIG. 1, and others with the first heat
exchanger 150a positioned as shown in FIG. 2, to provide simultaneous
heating and cooling. In any of these embodiments, the cooling process can
be used to liquefy methanol, and/or provide other functions. Such
functions can include liquefying or solidifying other substances, e.g.,
carbon dioxide, ethanol, butanol or hydrogen.

[0024] In particular embodiments, the reactants delivered to the reactor
110 are selected to include hydrogen, which is dissociated from the other
elements of the reactant (e.g. carbon, nitrogen, boron, silicon, a
transition metal, and/or sulfur) to produce a hydrogen-based fuel (e.g.
diatomic hydrogen) and a structural building block that can be further
processed to produce durable goods. Such durable goods include graphite,
graphene, and/or polymers, which may produced from carbon structural
building blocks, and other suitable compounds formed from hydrogenous or
other structural building blocks. Further details of suitable processes
and products are disclosed in the following co-pending U.S. patent
application Ser. Nos. ______ titled "CHEMICAL PROCESSES AND REACTORS FOR
EFFICIENTLY PRODUCING HYDROGEN FUELS AND STRUCTURAL MATERIALS, AND
ASSOCIATED SYSTEMS AND METHODS" (Attorney Docket No. 69545.8601US);
______ titled "ARCHITECTURAL CONSTRUCT HAVING FOR EXAMPLE A PLURALITY OF
ARCHITECTURAL CRYSTALS" (Attorney Docket No. 69545.8701US); and ______
titled "CARBON-BASED DURABLE GOODS AND RENEWABLE FUEL FROM BIOMASS WASTE
DISSOCIATION" (Attorney Docket No. 69545.9002US), all of which are filed
concurrently herewith and incorporated herein by reference.

[0025] FIG. 3 illustrates a system 300 having a reactor 310 with a movable
dish 321 configured in accordance another embodiment of the disclosed
technology. In a particular aspect of this embodiment, the reactor 310
includes a first reaction zone 311a and a second reaction zone 311b, with
the first reaction zone 311a receiving focused solar energy 127 when the
dish 321 has a first position, shown in solid ones in FIG. 3. The dish
321 is coupled to a dish actuator 331 that moves the dish 321 relative to
the reaction zones 311a, 311b. Accordingly, during a second phase of
operation, the controller 190 directs the dish actuator 331 to move the
dish 321 to the second position shown in dashed lines in FIG. 3. In one
embodiment, this arrangement can be used to provide heat to the second
reaction zone 311b when the dish 321 is in the second position. In
another embodiment, this arrangement can be used to cool the second
reaction zone 311b. Accordingly, the controller 190 can direct the
concentrator actuator 125 to point the dish 321 to a position in the sky
having lithe or no radiant energy, thus allowing the second reaction zone
311b to reject heat to the dish 321 and ultimately to space, in a manner
generally similar to that described above with reference to FIGS. 1 and
2.

[0026] In other embodiments, the systems can include solar collectors
having arrangements other than a dish arrangement. For example, FIG. 4
illustrates a system 400 having a reactor 410 that is coupled to a solar
concentrator 420 in the form of a trough 421. The trough 421 is rotated
by one or more trough actuators 431, and includes a concentrator surface
423 that directs incident solar energy 126 toward the reactor 410 for
heating. In a particular embodiment shown in FIG. 4, the reactor 410 can
include a first reaction zone 411a and a second reaction zone 411b that
can operate in a manner generally similar to that described above with
reference to FIGS. 1 and 2. The system 400 can further include a first
heat exchanger 450a that can be moved toward or away from a focal area
424 provided by the trough 421 at the underside of the reactor 410.
Accordingly, the first heat exchanger 450a can be positioned as shown
FIG. 4 when the incident solar energy 126 is directed to the first
reaction 411a for heating, and can be moved over the focal area 424 (as
indicated by arrows A) to reject heat in a manner generally similar to
that described above with respect to FIGS. 1 and 2. The reactor 410 can
include an insulator 430 positioned to prevent heat losses from the
reactor 410 during heating. The insulator 430 can also prevent heat from
leaving the reactor 410 other than along the emitted energy path 128, in
manner generally similar to that described above.

[0027]FIG. 5 is a partially schematic illustration of a system 500 that
includes a solar concentrator 520 having a Fresnel lens 521 positioned to
receive incident solar energy 126 and deliver focused solar energy 127 to
a reactor 510. This arrangement can be used in conjunction with any of
the systems and components described above for heating and/or cooling
constituents and/or components of the reactor 510.

[0028]FIG. 6 is partially schematic illustration of a system 600 having a
reactor 610 that receives radiation in accordance with still further
embodiments of the disclosed technology. In one aspect of these
embodiments, the reactor 610 can have an overall layout generally similar
to that described above with reference to FIGS. 1 and 2. In other
embodiments, the reactor can be configured like those shown in any of
FIGS. 3-5, with the components described below operating in a generally
similar manner.

[0029] The reactor 610 can include a transmissive component 612 that
allows focused solar energy 127 to enter a first reaction zone 611a. In
one embodiment, the transmissive component 112 includes glass or another
material that is highly transparent to solar radiation. In another
embodiment, the transmissive component 612 can include one or more
elements that absorb energy (e.g., radiant energy) at one wavelength and
re-radiate energy at another wavelength. For example, the transmissive
component 612 can include a first surface 613a that receives incident
solar energy at one wavelength and a second surface 613b that re-radiates
the energy at another wavelength into the first reaction zone 611a. In
this manner, the energy provided to the first reaction zone 611a can be
specifically tailored to match or approximate the absorption
characteristics of the reactants and/or products placed within the first
reaction zone 611a. For example, the first and second surfaces 613a, 613b
can be configured to receive radiation over a first spectrum having a
first peak wavelength range and re-radiate the radiation into the first
reaction zone 611a over a second spectrum having a second peak wavelength
range different than the first. The second peak wavelength range can, in
particular embodiments be closer than the first to the peak absorption of
a reactant or product in the first reaction zone 611a. Further details of
representative re-radiation devices are described in co-pending U.S.
patent application Ser. No. ______ titled "CHEMICAL REACTORS WITH RE
RADIATING SURFACES AND ASSOCIATED SYSTEMS AND METHODS" (Attorney Docket
No. 69545.8603US) filed concurrently herewith and incorporated herein by
reference.

[0030] In particular embodiments, the system can also include a radiation
control structure 660 powered by a control structure actuator 661. The
radiation control structure 660 can include multiple movable elements
662, e.g. panels that pivot about corresponding pivot joints 664 in the
manner of a Venetian blind. One set of elements 662 is shown in FIG. 6
for purposes of illustration--in general, this set is duplicated
circumferentially around the radiation-receiving surfaces of the reactor
610. Each movable element 662 can have a first surface 663a and a second
surface 663b. Accordingly, the radiation control structure 660 can
position one surface or the other to face outwardly, depending upon
external conditions (e.g. the level of focused solar energy 127), and/or
whether the reactor 610 is being used in a heating mode or a cooling
mode. In a particular aspect of this embodiment, the first surface 663a
can have a relatively high absorptivity and a relatively low emissivity.
This surface can accordingly readily absorb radiation during the day
and/or when the focused solar energy 127 is above a threshold level, and
can transmit (e.g., by conduction) the absorbed energy to the second
surface 663b. The second surface 663b can have a relatively low
absorptivity and a relatively high emissivity can accordingly emit energy
conducted to it by the first surface 663a. In one orientation, this
effect can operate to heat the first reaction zone 611a, and in the
opposite orientation, theis effect can operate to cool the first reaction
zone 611a (or another component of the reactor 110, e.g. the first heat
exchanger 150a described above), for example, at night. Accordingly, the
radiation control structure 660 can enhance the manner in which radiation
is delivered to the first reaction zone 611a, and the manner in which
heat is removed from the reactor 610.

[0031] In still further embodiments, the reactor 610 can include a
redirection component 670 coupled to a redirection actuator 671 to
redirect radiation that "spills" (e.g. is not precisely focused on the
transmissive component 612) due to collector surface aberrations,
environmental defects, non-parallel radiation, wind and/or other
disturbances or distortions. In a particular embodiment, the redirection
670 can include movable elements 672 that pivot about corresponding pivot
joints 674 in a Venetian blind arrangement generally similar to that
discussed above. Accordingly, these elements 672 can be positioned
circumferentially around the radiation-receiving surfaces of the reactor
610. In one aspect of this embodiment, the surfaces of the movable
elements 672 are reflective in order to simply redirect radiation into
the first reaction zone 611a. In other embodiments, the surfaces can
include wavelength-shifting characteristics described above and described
in co-pending U.S. patent application Ser. No. ______ titled "CHEMICAL
REACTORS WITH RE-RADIATING SURFACES AND ASSOCIATED SYSTEMS AND METHODS"
(Attorney Docket No. 69545.8603) previously incorporated by reference.

[0032] One feature of embodiments of the systems and processes described
above with reference to FIGS. 1-6 that they can use a solar collector or
concentrator surface to provide cooling as well heating, in effect,
operating the concentrator surface in reverse. This arrangement can
provide a useful heat transfer process for cooling products and/or other
constituents produced by the reactor, while reducing or eliminating the
need for separate elements (e.g., refrigeration systems) to provide these
functions.

[0033] Another feature of at least some of the foregoing embodiments is
that they can include surfaces specifically tailored to enhance the
absorption and/or emission of radiation entering or rejected by the
system. These elements can provide further thermodynamic efficiencies and
therefore reduce the cost of producing the reactants described above.

[0034] Certain aspects of the technology described in the context of
particular embodiments may be combined or eliminated in other
embodiments. For example, particular embodiments were described above in
the context of a reactor having two reaction zones. In other embodiments,
similar arrangements for rejecting heat can be applied to reactors having
a single reaction zone, or more than two reaction zones. The reaction
zone(s) can be used to process constituents other than those described
above in other embodiments. The solar concentrators described above can
be used for other cooling processes in other embodiments. The solar
concentrators can have other configurations (e.g., heliostat
configurations) in other embodiments. In at least some embodiments, the
reaction zone(s) can move relative to the solar concentrator, in addition
to or in lieu of the solar concentrator moving relative to the reaction
zone(s). The redirection component and radiation control structures
described above can be used alone, in combination with each other, and/or
in combination with any of the arrangements described above in
association with FIGS. 1-5.

[0035] Further, while advantages associated with certain embodiments of
the technology have been described in the context of those embodiments,
other embodiments may also exhibit such advantages, and not all
embodiments need necessarily exhibit such advantages to fall within the
scope of the present disclosure. Accordingly, the present disclosure and
associated technology can encompass other embodiments not expressly shown
or described herein.